Which update should I do next?

1. Marketplace [2 weeks dev time]
2. New event items [2 days dev time]
3. Alliances (multiple teams become one alliance) [2 days dev time]
4. Upgrade chest and bag user interface [1 day dev time]
5. Graphical update for team battle to look like Famicon Wars [1 week dev time]
6. IOS app [1 month dev time]